Plasma processing method

1. A plasma processing method for carrying out plasma processing on a wafer under Run-to-Run control by using a plasma processing apparatus having a plasma processing chamber in which plasma processing is carried out, a process monitor which monitors a condition in the plasma processing chamber, and an actuator which controls parameters which are constituent elements of a plasma processing condition, the method comprising the steps of: making one of the parameters a (N−1)th manipulated variable; calculating a first difference between a process monitor value in the plasma processing obtained by the process monitor and a desired value of the process monitor value in the plasma processing; calculating a correction amount of the (N−1)th manipulated variable on the basis of the first difference and a previously obtained correlation between the process monitor value in the plasma processing and the (N−1)th manipulated variable; wherein N is a natural number equal to or larger than 2, determining whether or not the (N−1)th manipulated variable exceeds a limit value of the (N−1)th manipulated variable on the basis of the correction amount of the (N−1)th manipulated variable; calculating an Nth difference between the monitor value in the plasma processing and a monitor value calculated, as a case that the (N−1)th manipulated variable is a limit value, from the previously obtained correlation between the monitor value in the plasma processing and the (N−1)th manipulated variable; and calculating a correction amount of the Nth manipulated variable on the basis of the previously obtained correlation between the monitor value in the plasma processing and the Nth manipulated variable and the Nth difference; and wherein determining that the (N−1)th manipulated variable exceeds a limit value of the (N−1)th manipulated variable on the basis of the correction amount of the (N−1)th manipulated variable, correcting a plasma processing condition of a next wafer on the basis of the correction amount of the (N−1)th manipulated variable which causes the (N−1)th manipulated variable to be set to the limit value of the (N−1)th manipulated variable and the correction amount of the calculated Nth manipulated variable.

2. The plasma processing method according to claim 1 , further comprising the steps of: determining whether or not the Nth manipulated variable exceeds a limit value of the Nth manipulated variable on the basis of the correction amount of the Nth manipulated variable; calculating an (N+1)th difference between the monitor value in the plasma processing and a monitor value calculated, as a case that the Nth manipulated variable is a limit value, from the previously obtained correlation between the monitor value in the plasma processing and the Nth manipulated variable; and calculating a correction amount of the (N+1)th manipulated variable on the basis of the preciously obtained correlation between the monitor value in the plasma processing and the (N+1)th manipulated variable and the (N+1)th difference, and wherein, when determining that the (N−1)th manipulated variable exceeds the limit value of the (N−1)th manipulated variable on the basis of the correction amount of the (N−1)th manipulated variable, and determining that the Nth manipulated variable does not exceed the limit value of the Nth manipulated variable on the basis of the correction amount of the Nth manipulated variable, setting the correction amount of the (N+1)th manipulated variable to zero, and correcting the plasma processing condition of the next wafer on the basis of the correction amount of the (N−1)th manipulated variable which causes the (N−1)th manipulated variable to be set the limit value of the (N−1)th manipulated variable and the correction amount of the calculated Nth manipulated variable.

3. The plasma processing method according to claim 1 , wherein the N is 2, and the plasma processing is a plasma etching.

4. The plasma processing method according to claim 2 , wherein the N is 2, and the plasma processing is a plasma etching.

5. The plasma processing method according to claim 3 , wherein the (N−1)th manipulated variable is a flow rate of a gas provided in the plasma processing chamber.

6. The plasma processing method according to claim 3 , wherein one of the (N−1)th and the Nth manipulated variable is a flow rate of a gas provided in the plasma processing chamber.

7. The plasma processing method according to claim 5 , wherein the other of the (N−1)th and the Nth manipulated variable is a radio frequency bias power provided in the plasma processing chamber.